Assessment of the systemic immune‐inflammation index in type 2 diabetic patients with and without dry eye disease: A case‐control study

Abstract Background The inflammation plays a role in the pathophysiology of type‐2 diabetes progression, and the mechanism remains unclear. The systemic immune‐inflammation index (SII) is a novel inflammatory marker for type 2 diabetes patients and integrates multiple indicators in complete blood counts and routine blood tests. Aim Since there is no international diagnostic standard for dry eye disease (DED), this study uses low‐cost inflammatory blood biomarkers to investigate the correlation between SII and DM2–DED and determine the diagnosis indices of other biomarkers in DM2–DED. Methodology A case‐control retrospective analysis of totel patients n = 293 randomly selected and categorized into four groups: DED, DM2, DM2‐DED, and healthy subjects. Demographic and blood biomarker variables were classified as categorical and continuous variables. The platelet‐to‐lymphocyte ratio (PLR), lymphocytes‐to‐lymphocyte ratio, neutrophil‐to‐lymphocyte ratio (NLR), and SII were calculated platelet count multiply by NLR and analyzed for their correlation for all groups. Results Focusing on DM2‐DED patients was more common in females, 59.6%, than in males, 40.2%. The mean ages were 60.7 ± 11.85 years, a statistically significant difference with all groups. In the study group DM2‐DED, there was an increase in all blood markers compared to all remaining groups except PLR. Only neutrophil, hemoglobin A1c (HbA1c), and fasting blood sugar levels were statistically significant differences in DM2‐DED patients (p > 0.001, p < 0.001, and p < 0.001, respectively) compared to all groups. There was a positive correlation between HbA1c and PLR, HbA1c and NLR, and HbA1c and SII (r = 0.037, p = 0.705; r = 0.031, p = 0.754; and r = 0.066, p < 0.501, respectively) in the DM2‐DED group. Conclusion This study demonstrated that elevated SII values were linked to elevated HbA1c in DM2‐DED patients. The potential of SII and HbA1c as early diagnostic indicators for ocular problems associated with diabetes mellitus is highlighted by their favorable connection in diagnosing DM2‐DED.

diagnostic indicators for ocular problems associated with diabetes mellitus is highlighted by their favorable connection in diagnosing DM2-DED.

| INTRODUCTION
Dry eye disease (DED) is a common inflammatory disorder of the tear film among adults worldwide.It frequently arises in conjunction with other illnesses, as a result of environmental stimuli, or even due to the use of some medications, such as antihistamines, which are available over the counter.It can also occur due to ocular surgery, computer screen exposure, or the use of contact lenses. 1 DM has long been linked to an increased risk of the development of chronic ocular disorders such as DED. 2,3The prevalence of DED is 15%−33% in diabetic patients over 65 years of age and is 50% more common in women than men. 4 In patients with DM, decreased corneal sensitivity and poor reflex-induced tear secretion may also contribute to developing DED.Additionally, oxidative stress induces by diabetes which contribute in developping DED.Previous studies have examined the relationship.In a hospital-based study, 54% of people with diabetes had DED, and a statistically significant difference correlation was found between the durations of DM and DED. 5 Eventually, uncontrolled DM with DED (DM-DED) causes visual impairment and corneal erosions, leading to secondary microbial infections. 6DED is frequently associated with a disruption of the corneal epithelium, which, in turn, opens the door to microbial invasion and can lead to microbial keratitis. 7,8To our knowledge, the degree to which DM may increase the chance of developing DED is unknown.
Blood biomarkers are used to detect microbial invasions.An improved understanding of the blood biomarkers associated with DM2-DED and their influence on the disease pathophysiology would aid in the early detection, diagnosis, and management of the disease.
DED is associated with raised levels of glycated hemoglobin A1c (HbA1c). 9Inflammation and immunity have both been implicated in the pathogenesis of DED.Hyperglycemia triggers an inflammatory cascade in the lacrimal functional unit, which then triggers both innate and adaptive immune responses. 10Nevertheless, few studies have been performed to investigate the exact mechanisms that underlie the onset of diabetes-induced DED, the associated risk factors, or hematological changes associated with inflammatory mediators that could be used as biomarkers. 1 The levels of production of inflammatory cytokines such as interleukin (IL)-1α, IL-1β, tumor necrosis factor-A, and matrix metalloproteinase-9 have been implicated in the pathophysiology of DED. 11Also, levels of IL-6, IL-8, and vascular endothelial growth factor in serum and vitreous fluid are increased in DM patients as compared to healthy people. 12However, the measurement of inflammatory cytokines is costly and not commonly used in daily clinical practice.Also, routine blood biomarkers, like the complete blood counts, including counts of platelets, neutrophils, and lymphocytes, have been demonstrated in numerous DED studies to be useful in assessing inflammation levels.Ozarslan et al. studied several blood parameters that were compared between the healthy group and patients with DED; the results were statistically significant differences in levels of white blood cells and C-reactive protein (CRP). 13As inflammation is also involved in the development of DM2, it is, therefore, likely that DED occurs more frequently in DM2 patients. 14,15Interestingly, Alhalwani et al. noted a positive correlation between neutrophil-to-lymphocyte ratio (NLR) and CRP to albumin ratio (CAR) in DM2 patients with DED. 16[22][23][24] Two low-cost indices, NLR and PLR, have been repeatedly assessed for their efficacy as diagnostic and prognostic tools for DED, DM, and other diseases.Raised levels of NLR and PLR have been associated with DED. 25 The value of the systemic immuneinflammation (SII) index has been used as a prognostic indicator for inflammatory diseases such as DM2. 26The combination of NLR, PLR, and SII measurements has proven more specific than testing for inflammatory biomarkers such as CRP. 27However, according to Meng et al., NLR, but not PLR, can be used to evaluate the severity of DED in diabetic patients.A recent study found a correlation between SII and type 2 diabetic retinopathy patients. 28Another study shows that SII level is increased among diabetes population. 29Therefore, this research aimed to elucidate further the association between systemic inflammatory biomarkers NLR, PLR, and SII (as immune response-related indices) in DM2-DED patients to improve our comprehension of DED's pathogenesis, treatment, and prevention.

| Study subject and sampling
For this research, a retrospective case-control study included patients who had visited the King Abdulaziz Medical City (KAMC) outpatient clinic between January 2018 and December 2020.The information on healthy subjects was collected from the blood donation center.In total, 293 patients were included in this study; the study group was selected based on all patients with complete laboratory parameters DM2-DED (n = 107).However, the control groups were selected randomly; DED only (n = 52), DM2 only (n = 78), and healthy (n = 56) groups (Figure 1).We found that the SII is an independent value that would be used as a predictor and prognostic marker in a group of patients with DM2-DED compared to three control groups comprising patients with DED only, patients with DM2 only, and healthy subjects.Selection criteria for all participants included in the study criteria were that patients could be of either gender, must be 18 years of age or older, with eye diseases other than DED were excluded.Patients have either DM2, DED, or both, according to the group to which they would be allocated.Since the normal range for HbA1c is HbA1c ≤5.7%, subjects who were healthy or DED and had an HbA1c higher than 5.8% were excluded.Similarly, patients with diabetes with an HbA1c greater than 6.5%, including DM2 and DM2-DED patients, were excluded if their HbA1c was less than 5.5%.
The participants in the study group who met these criteria were randomly selected for each group.Each of the four groups contained at least 50 subjects.The sample size of the study group was determined based on available D2M-DED patients.

| Sample size and data sheet
Data retrieved from patient files via the BESTCare 2.0A system were entered into Microsoft Excel.Sample sizes were calculated using an online clinical sample size calculator. 30Some 12,000 patients with DM2 and DED attended the KAMC outpatient clinic between January 2018 and December 2020.It was estimated that the required sample size should show a power of 80% and a significance of p = 0.05.The most recent prevalence of DED among patients with DM2 was estimated to be 54.3%. 31Accordingly, this case-control study's minimum required sample size was 329 patients.This study had 107 individuals, the only DM2-DED patients with complete data, and met the inclusion criteria.
The data collection sheet consisted of demographics (age and gender) and variables for the study and control groups, which ascertained the presence of DM2, other health problems, neutrophil count, lymphocyte count, platelet count, fasting blood glucose (FBS), and HbA1c levels.NLR, PLR, and SII indices were calculated and correlated with the presence of DED, DM2, DM2-DED, or control subjects.NLR was computed by dividing the neutrophil count (×10 9 /L) by the lymphocyte count (×10 9 /L); PLR was computed by dividing the platelet count (×10 9 /L) by the lymphocyte count (×10 9 /L); and SII was computed by multiplying the platelet count (×10 9 /L) by NLR. 32

| Statistical analyses
All statistical analyses were carried out using Statistical Package for Social Science (SPSS) software, version 20.0 (IBM Corp.).For descriptive statistics, frequencies and percentages were computed for such categorical variables as gender.For inferential statistics, gender and condition frequencies were compared by application of the χ 2 test.The one-way analysis of variance ANOVA test was used to compare ages among all groups and 95% confidence intervals (CIs) were calculated for all variables.While the laboratory findings data was confirmed to be nonparametric, this report presents the data using mean and standard deviation (mean ± SD) for better readability and ease of interpretation.However, recognizing the nonparametric nature of the data, the Kruskal−Wallis test was applied to assess statistical differences between groups based on median.Spearman's correlation test was used to assess the correlation among factors.A threshold for significance was set at p ≤ 0.05.The more information in supplamental materials as shown in Supporting Information S1: F I G U R E 1 Flowchart of the collection of participants in the study.KAMC, King Abdulaziz Medical City.
In the comparison between all groups, there was a statistically significant difference increase in levels of neutrophils, HbA1c, and FBS (p < 0.001, p < 0.001, p < 0.001, p < 0.001, and p = 0.05, respectively).
The mean values for lymphocytes, platelets, PLR, NLR, and SII among all groups diverged widely, although the differences were not a statistically significant difference (p = 1.004, p = 1.461, p = 0.291, p = 0.299, and p = 0.271, respectively).This finding showed that the SII was a betterdifferentiating index among all groups than PLR and NLR.Both groups (DM2 and DM2-DED) have higher SII values (537.9 and 545.4,respectively) and HbA1c levels (9.2 ± 7.90% and 8.7 ± 1.60%, respectively) as compared to the DED and healthy groups.

| Correlation study
Correlation analysis for each group of the HbA1c against the PLRs, NLRs, and SII is shown in Figure 2. In the DM2-DED group, there were positively correlated results between the HbA1c versus each of the PLR, NLR, and SII variables with no staticly significant diffrences (p = 0.705, p = 0.754, and p = 0.501, respectively), more information in supplamental materials as shown in Supporting Information S1: Table 2.

| DISCUSSION
To our knowledge, this research revealed the first study evaluating the SII levels in patients with DM2-DED compared to DED, DM2, and healthy controls.Although the dey eye disease progression and risk factors of type 2 diabetes patients have not been fully understood.
The subjects of this study were healthy patients with type 2 diabetes and DED with mean ages in the elderly range, with females being older than males.[35] Because both PLR and NLR have previously been used as markers for inflammation. 36,371][42][43] Based on that, this study employed PLR, NLR, and SII laboratory findings for patients with DM2-DED, alongside, although few studies have been carried out to investigate the association of DM2 with DED patients, further investigation is required. 4,16,31,33,44,45 the DM2-DED study group, the means of PLR and NLR levels were higher than the healthy control group.However, there was no significant difference in the NLR, PLR, and SII of individuals between all groups, so we assume that this did not affect the study's outcome.Interestingly, the DM2-DED group outperforms the healthy group in NLR but not PLR.This outcome is consistent with a study that Meng et al. published, which indicated that the NLR, but not the PLR, of DED patients was reportedly higher than that of healthy subjects. 25Also, NLR and PLR value are dependent on population characteristics such as race. 38,57e DM2-DED had increased levels of SII as well as HbA1c.In addition, SII values were found to be considerably higher in patients with DM2-DED and DM2 than healthy and DED only.This finding aligns with many studies on chronic diseases compared with healthy subjects.A study reported that PLR, NLR, and SII levels were higher than the healthy control group in numerous earlier investigations on inflammatory diseases, including hepatocellular carcinoma and diabetic depression. 26[60] Also, all groups' SII results were higher than those of the healthy group, consistent with other research linking elevated SII levels to inflammatory diseases such as diabetes only, and DED only. 13,42,47,58 the study by Ozarslan Ozcan et al., DED patients showed significantly higher SII, PLR, and NLR levels than the healthy group.
Additionally, a diabetic study has examined the links between patients' NLR levels and those of blood glucose, and their findings are consistent with our findings in DM2-DED patients. 61perglycemia is related to the elevated production of reactive oxygen species from neutrophils, which in turn reflects alterations to neutrophil clearance and function and prolonged inflammation. 61The elevated SII was supported by poor HbA1c levels and recurrence in patients with DM2 and DM2-DED.Additionally, recently published work showed a relationship between HbA1c and SII (r's = 0.145, p = 0.01).In contrast, SII supersedes NLR and PLR as a prognostic factor for DM2-DED outcomes.The results were satisfactory and suggested that DM2 patients with poor glycaemic control demonstrated glucose levels that made them susceptible to DED. 5 DM2 patients with poor HbA1c levels had more risk factors for DED. 31 This study supported our findings that SII values were higher in those patients with DM2 and DM2-DED, who are characterized by poor HbA1c levels compared to healthy and DED groups.
In light of the correlation findings, a combination of both SII and HbA1c may be suitable biomarker for the pathogenesis and prediction of the disease of DM2-DED.This study adds new information to understanding the role of inflammation in the pathophysiology of DM2-DED.A potential explanation of a better prognostic value might be that SII was more comprehensive in reflecting the status of inflammatory and immune responses than the other established factors.

| CONCLUSION
In conclusion, this study supports the idea that inflammation may play an essential role in the development of diabetic patients presenting with DED.The results of our study indicate that SII levels are differences between all groups DM2-DED, DED, DM2, and healthy subjects.Additionally, SII has higher value compared to NLR and PLR among all groups, which consider an inflammatory indicator.
There is a positive correlation between HbA1c levels and SII in the DM2-DED group than in other groups.Moreover, our study demonstrated that higher SII may be a potential marker for DM2-DED development.These findings, however, indicate that additional investigation is required to discover other potential biomarkers that can be used to identify and prevent the early stages of DED in DM2 patients.

| LIMITATIONS
The ability of this investigation to evaluate the severity of DED is constrained by the absence of relevant retrospective data.However, additional prospective, randomized controlled studies involving a larger patient population are required to generate more robust data.
B) the age mean and SDs in years of all patients, showing a statistically significant difference arising between DED (48.7 ± 16.72 years), DM2 patients (59.1 ± 14.3 years), DM2-DED patients (60.7 ± 11.85 years), and healthy subjects (53.9 ± 6.35 years) as evaluated by the post hoc Tukey HSD multiple-comparison test (p < 0.001), more information in supplamental materials as shown in Supporting Information S1: Table

F I G U R E 2
Correlation between HbA1c and PLR (A), HbA1c and NLR (B), and HbA1c and SII (C) for the study and control groups.HbA1c, hemoglobin A1c; NLR, neutrophil-to-lymphocyte ratio; PLR, platelet-to-lymphocyte ratio; SII, systemic immune-inflammation index.Studies related to DED patients only, the study findings reported by Meng et al., which showed that PLR (117.48 ± 54.68) and NLR (2.59 ± 1.25) in the DED group were higher than the healthy control group PLR (115.48 ± 54.33) and NLR (2.20 ± 1.24) values.
Despite the discrepancy, our study verified the findings of Ozarslan Ozcan et al., which showed a positive correlation between SII, the NLR, and PLR biomarkers.According to Atak et al.'s study of DM2 patients, a positive correlation exists between PLR and HbA1c levels, supporting our findings that PLR levels are positively correlated with HbA1c levels in the DM2-DED group.22